U.S. patent application number 12/367339 was filed with the patent office on 2009-07-02 for method, system and apparatus for protecting wavelength division multiplex transmission.
This patent application is currently assigned to Huawei Technologies Co., Ltd.. Invention is credited to Ming CHEN, Bin HONG, Hanguo LI.
Application Number | 20090169200 12/367339 |
Document ID | / |
Family ID | 38076707 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090169200 |
Kind Code |
A1 |
LI; Hanguo ; et al. |
July 2, 2009 |
METHOD, SYSTEM AND APPARATUS FOR PROTECTING WAVELENGTH DIVISION
MULTIPLEX TRANSMISSION
Abstract
A method for protecting WDM transmission. On the first
transmission direction, the first node implements service
transmission to the second node by selecting one from the two
transmission paths protected by each other, the second node
implements two-path reception based on the two transmission paths;
on the second transmission direction contrary to the first
transmission direction, the second node implements two-path service
sending via the two transmission paths protected by each other, the
first node implements reception by selecting one from the two
transmission paths. A system for implementing the WDM transmission
protection and an apparatus thereof.
Inventors: |
LI; Hanguo; (Shenzhen,
CN) ; CHEN; Ming; (Shenzhen, CN) ; HONG;
Bin; (Shenzhen, CN) |
Correspondence
Address: |
Leydig, Voit & Mayer, Ltd;(for Huawei Technologies Co., Ltd)
Two Prudential Plaza Suite 4900, 180 North Stetson Avenue
Chicago
IL
60601
US
|
Assignee: |
Huawei Technologies Co.,
Ltd.
Shenzhen
CN
|
Family ID: |
38076707 |
Appl. No.: |
12/367339 |
Filed: |
February 6, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2007/070380 |
Jul 30, 2007 |
|
|
|
12367339 |
|
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Current U.S.
Class: |
398/7 ;
398/79 |
Current CPC
Class: |
H04J 14/0227 20130101;
H04J 14/0282 20130101; H04J 14/0294 20130101; H04J 14/0295
20130101; H04J 14/025 20130101; H04J 14/0283 20130101; H04J 14/0297
20130101; H04J 14/0246 20130101 |
Class at
Publication: |
398/7 ;
398/79 |
International
Class: |
H04J 14/02 20060101
H04J014/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2006 |
CN |
200610110579.2 |
Claims
1. A method for protecting Wavelength Division Multiplex, WDM,
transmission, comprising, transmitting, by a first node, a service
to a second node via one path selected from two transmission paths
protected mutually in a first transmission direction; and
receiving, by the second node, the service via the two transmission
paths in the first transmission direction; and transmitting, by the
second node, a service to the first node via two transmission path
protected mutually in a second transmission direction opposite to
the first transmission direction; and receiving, by the first node,
the service via one path selected from the two transmission paths
in the second transmission direction.
2. The method according to claim 1, wherein the first node is a
center node in a WDM transmission system; and the second node is a
distributor node in the WDM transmission system.
3. The method according to claim 2, wherein the transmission
process in the first transmission direction comprises,
transmitting, by the center node, a service to the distributor node
via one path, as a working path carrying the service, selected from
the two transmission paths protected mutually from the center node
to the distributor node; and receiving, by the distributor node,
the service carried in the two permanently connected transmission
paths from the center node to the distributor node.
4. The method according to claim 2, wherein the transmission
process in the second transmission direction comprises,
transmitting, by the distributor node, a service to the center node
via the two transmission paths protected mutually between the
distributor node and the center node respectively; and
transmitting, by the center node, the service to customer side via
a path selected from the two transmission paths as a working
path.
5. The method according to claim 4, further comprising, in the
first transmission direction, transmitting, by the second node, the
service to a third node upon reception of the service from the
first node; and in the second transmission direction, receiving, by
the second node, the service from the third node before
transmitting a service to the first node via two transmission path
protected mutually by the second node.
6. The method according to claim 2, further comprising, performing,
by the first node, selective switching for the transmission path in
the first transmission direction based on path fault information in
the first transmission direction fed back by the third node via the
path in the second transmission direction.
7. The method according to claim 6, wherein the process for
performing selective switching for the transmission path in the
first transmission direction by the first node comprises,
detecting, by the third node, if there occurs a fault in the
service in the first transmission direction; transmitting, by the
third node, path fault information in the first transmission
direction to the first node via the path in the second transmission
direction, upon detection of a fault occurring in the service in
the first transmission direction; and switching, by the first node,
the service in the first transmission path from the working path to
a backup path between the two transmission paths protected
mutually.
8. The method according to claim 5, wherein the third node is a
terminal node.
9. The method according to claim 4, further comprising, detecting,
by the first node, if there occurs a fault in the service in the
second transmission direction; and performing, by the first node,
selective switching for the receiving path in the second
transmission path, upon detection of a fault occurring in the
service in the second transmission direction.
10. A system for protecting Wavelength Division Multiplex, WDM,
transmission, comprising a first node and a second node connected
with each other via an optical fiber in the WDM system, wherein,
the first node comprises, a selective-transmission module adapted
to transmit a service to a second node via one path selected from
two transmission paths protected mutually in a first transmission
direction, and a selective-reception module adapted to receive a
service from the second node via one path selected from two
transmission paths protected mutually in a second transmission
direction; wherein the second transmission direction is opposite to
the first transmission direction; the second node comprises, a
dual-reception module adapted to receive the service from the first
node via the two transmission paths protected mutually in the first
transmission direction; and a dual-transmission module adapted to
transmit the service to the first node via the two transmission
paths protected mutually in the second transmission direction.
11. The system according to claim 10, wherein the first node is a
center node and the second node is a distributor node.
12. A device for protecting Wavelength Division Multiplex, WDM,
transmission, comprising, a dual-reception module adapted to
receive a service via two transmission paths protected mutually in
a first transmission direction; and a dual-transmission module
adapted to transmit a service via two transmission paths protected
mutually in a second transmission direction; wherein the second
transmission direction is opposite to the first transmission
direction.
13. The device according to claim 12, wherein the dual-reception
module is a dual-reception permanent bridge connector; and the
dual-transmission module is a dual-transmission permanent bridge
connector.
14. The device according to claim 13, wherein the device is a
distributor node in a WDM system.
15. A device for protecting Wavelength Division Multiplex, WDM,
transmission, comprising, a selective-transmission module adapted
to transmit a service via one path selected from two transmission
paths protected mutually in a first transmission direction; and a
selective-reception module adapted to receive a service via one
path selected from two transmission paths protected mutually in a
second transmission direction; wherein the second transmission
direction is opposite to the first transmission direction.
16. The device according to claim 15, wherein the
selective-transmission module and the selective-reception module
each are a selective switch module.
17. The device according to claim 16, wherein the device is a
center node in a WDM system.
18. A system for protecting Wavelength Division Multiplex, WDM,
transmission, comprising a center node, a distributor node and a
terminal node; wherein the distributor node is connected with the
center node via a backbone optical fiber, and the distributor node
is connected with the terminal node via a distribution optical
fiber; wherein, the distributor node comprises two or more
permanent bridge connectors, and at least two of which are
respectively used for a dual-reception downstream service and a
dual-transmission upstream service.
19. The system according to claim 18, wherein the permanent bridge
connector is a coupler.
20. The system according to claim 18, wherein, the center node
comprises a downstream transmitter, an upstream receiver, a first
selective switch module, a second selective switch module, a first
Wavelength Division Multiplexer/De-Multiplexer and a second
Wavelength Division Multiplexer/De-Multiplexer; an input of the
first selective switch module is connected with the downstream
transmitter, and two outputs of the first selective switch module
are connected with the first Wavelength Division
Multiplexer/De-Multiplexer and the second Wavelength Division
Multiplexer/De-Multiplexer respectively; two inputs of the second
selective switch module are respectively connected with the first
Wavelength Division Multiplexer/De-Multiplexer and the second
Wavelength Division Multiplexer/De-Multiplexer, and an output of
the second selective switch module is connected with the upstream
receiver.
21. The system according to claim 20, wherein the first selective
switch module and the second selective switch module each are an
optical switch or an electrical switch.
22. The system according to claim 21, wherein the terminal node
comprises a downstream service receiver and an upstream service
transmitter; dual-transmission permanent bridge connector of the
distributor node.
23. A method for protecting Wavelength Division Multiplex, WDM,
transmission, comprising, detecting, by a terminal node whether a
fault occurs in a downstream service; identifying, by the terminal
node, a downstream path in which the fault occurs and generating
downstream path fault information, when the fault occurring in the
downstream service is detected; transmitting, the downstream path
fault information to a center node via an upstream path; and
switching, by the center node, the downstream service from a
working path to a backup path.
24. The method according to claim 23, wherein the detecting whether
a fault occurs in the downstream service by the terminal node
comprises, detecting, by the terminal node, the power of part of
the downstream service signal split from that to be inputted to the
receiving end, or detecting the fault directly using a receiver, or
detecting overhead of the downstream service for detecting the
fault.
25. The method according to claim 24, wherein, the downstream path
fault information is transmitted to the center node via overhead
information of an upstream service wavelength; or the downstream
path fault information is transmitted to the center node via an
optical monitoring channel; or the downstream path fault
information is transmitted to the center node via an alarm byte in
the upstream service.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International Patent
Application No. PCT/CN2007/070380, filed Jul. 30, 2007, which
claims priority to Chinese Patent Application No. 200610110579.2,
filed Aug. 9, 2006, both of which are hereby incorporated by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to the transmission of
communication field, and in particular, to a method, a system and a
device for protecting Wavelength Division Multiplex (WDM)
transmission in Metro Access Network.
BACKGROUND OF THE INVENTION
[0003] In the Metro Access Network, Passive Optical Network (PON)
is a most popular fiber access approach conventionally. However,
with an optical fiber, the highest speed of only 1.25 Gbps or 2.5
Gbps may be supported, while, in practice, the speed of a network
card commonly used in a computer of a user is up to 100 Mbps, and
the access bandwidth is only 2 Mbps may be provided, which may not
satisfy the increasing demands of the customers. As a result, a
fiber access with higher bandwidth is required. WDM technologies
have already been commercialized for use in large scale in Backbone
Network and Metro Area Network (MAN), and its bandwidth may be
upgraded and expanded continuously by adding wavelengths with the
demands. With the fast increase of the access bandwidth, it has
been a trend for WDM technologies to be applied to the access
layer. While, conventionally, Point-to-Point transmission is used
in WDM technologies, which results in a high cost for applying WDM
technologies on the access layer. Therefore, a new technology is
needed to reduce the application cost. In the conventional art, a
combination of WDM technologies and PON technologies is commonly
used, as shown in FIG. 1, there are respectively a plurality of n
downstream transmitters and n upstream receivers at a center node,
which are respectively used for transmitting an optical wavelength
service in the downstream path and for receiving an optical
wavelength service in the upstream path. The optical wavelength
service in the downstream path first passes through a Wavelength
Division Mux/DeMux, and transmits to another Wavelength Division
Mux/DeMux at a distribution node via a backbone fiber, and then
inputs into a downstream receiver at a terminal node respectively.
The same approach is used for the transmission of an optical
wavelength service in the upstream path. As can be seen from the
description for FIG. 1, different wavelengths may be utilized by
terminal nodes in WDM-PON solutions in the conventional art, which
provides more bandwidths for use.
[0004] When, in practice, a WDM transmission system is used in a
real network, because a large amount of customers' data is carried
in the WDM transmission system which provides a plurality of
wavelengths, and a bandwidth per wavelength for data transmission
is in an order of Gbps magnitude, once a fault occurs, services of
important customers or many other customers may possibly be
impacted seriously, which accordingly causes a big loss to the
Carriers. Therefore, the WDM transmission system requires to be
protected for providing a higher reliability. In general, in a
network, it is in the transmission medium, i.e., an optical fiber,
that a fault always occurs. For example, there occurs a case that
the optical fiber in the underground fiber cables are cut off
during municipal constructions or the construction of a new
building, which accordingly causes a fault of network connection
occurs. As a result, the Carrier requires a reliable technique for
protecting the wavelength services.
[0005] The network protection techniques generally used include:
dual-transmission-selective-reception path dedicated protection
with 1+1, path-shared protection with 1:1 or M:N, and Multiplex
Section Protection (MSP), among which the
dual-transmission-selective-reception path dedicated protection
with 1+1 is a most commonly used scheme. In the
dual-transmission-selective-reception path dedicated protection
with 1+1 scheme, a working path and a backup path with different
routings are used for transmitting the services to be protected,
and the backup path is not used for transmitting other services.
When fault occurs in transmission lines, it will be detected by the
monitoring point corresponding to the service connections, so that
the services may be switched from the working path to the backup
path automatically depending on the fault type and the protection
scheme to ensure the availability of the service.
[0006] The structure diagram of the
dual-transmission-selective-reception path dedicated protection
with 1+1 is shown in FIG. 2 where a permanent bridge connection is
used. A downstream and upstream, two-way service signals exist
between a transmitting-end node A and a receiving-end node B, both
of which have a working path and a backup path. The downstream
service signal at node A first passes through a
permanent-bridge-connection splitter (such as an optical coupler)
which splits the service signal sent from the transmitting-end node
A into totally the same two-way signals which respectively are
transmitted via the working path and the backup path; and a
selector (such as an optical switch) is used at the receiving-end
node B for selecting one of the two-way signals. The protection
switching of the upstream service signal may be realized in the
same way as above stated.
[0007] Now an example is provided with a downstream service from
the node A to the node B. Because the node B detects the services
both in the working path and in the backup path simultaneously, and
when a fault occurs in the working path and is detected by the node
B, the fault is reported and the selective switch of the node B is
controlled to be switched from the working path to the backup path
so as to realize the protection of the service. The fault detection
and the switching are performed at a same node without informing
another node; therefore, the interaction of messages is not
required between two nodes via communication protocols. This way is
referred as a single-end switch. Similarly, a same mechanism is
used for the service from the node B to the node A.
[0008] In the conventional art, the single-end switch mode, in
which both the detection and switching are made at the receiving
end, is used for the 1+1 protection scheme, and a permanent bridge
connection is made at the transmitting end. In this mode, a device
for switching selection is required at the receiving end. When this
scheme is applied in a bi-directional transmission network, a power
supply is required at the both end nodes. When the scheme is
applied in a Metro Access Network, power must be supplied at the
switching node if the downstream path is required to be protected.
If only the fiber from the center node to the distribution node in
FIG. 1 is to be switched with protection, the distribution node
shall works in active mode; therefore, a Passive Optical Network
(PON) technique may not be implemented.
[0009] In the optical fiber access, the optical fiber is connected
from the center node to a number of buildings or residential areas,
and then connected to the devices in the machine room of the
residential areas or the buildings. In real network constructions,
fibers are commonly laid by the side of road or the building in
advance; and when there presents a user in the areas and the
buildings, the optical fiber is connected with the laid fibers.
Because a device requiring a power supply may not be used for the
distribution in the middle, a fiber distribution node by the side
of road or building is required to be a passive distributor device,
while the center node and the terminal node at the ends of the
fiber may be supplied with power in the machine room.
[0010] Power may be supplied both at the center node and the
terminal node, while the distributor node, which is generally
placed by the side of road or at a relatively simple environment,
has no power supply. If dual-transmission-selective-reception of
the downstream service is to be performed, a power supply is
required to be provided at this distributor node for implementing
switching action of an optical switch or an electrical switch. In
order to guarantee the reliability of the equipment, peripheral
devices, such as air conditioners are always needed to ensure the
environment temperature and moisture under which the equipment and
devices run may meet the requirements of the reliability thereof,
which accordingly causes a huge cost for the construction of the
distributor node.
SUMMARY OF THE INVENTION
[0011] An embodiment of the invention provides a method, a system
and a device for protecting WDM transmission, which may actualize a
passive distributor node so as to reduce the total cost of network
construction.
[0012] An embodiment of the invention provides a method for
protecting WDM transmission, where in a first transmission
direction, a first node transmits a service to a second node via
one path selected from the two transmission paths protected
mutually, and the second node receives the service in the two
transmission paths, i.e., performs a dual reception; in a second
transmission direction opposite to the first transmission
direction, the second node transmits a service to the first node
via two transmission path protected mutually, i.e., performs a dual
transmission, and the first node receives the service via one path
selected from the two transmission paths.
[0013] An embodiment of the invention further provides a system for
protecting WDM transmission, which includes a first node and a
second node connected with each other via an optical fiber in the
WDM system; the first node includes, a selective-transmission
module adapted to transmit a service to a second node via one path
selected from two transmission paths protected mutually in a first
transmission direction, and a selective-reception module adapted to
receive a service from the second node via one path selected from
two transmission paths protected mutually in a second transmission
direction; the second transmission direction is opposite to the
first transmission direction; the second node includes, a
dual-reception module adapted to receive the service from the first
node via the two transmission paths protected mutually, i.e.,
perform a dual reception, in the first transmission direction; and
a dual-transmission module adapted to transmit the service to the
first node via the two transmission paths protected mutually, i.e.,
perform a dual transmission, in the second transmission
direction.
[0014] An embodiment of the invention further provides a device for
protecting WDM transmission, which includes, a dual-reception
module adapted to receive a service in two transmission paths
protected mutually, i.e., perform a dual reception, in a first
transmission direction; and a dual-transmission module adapted to
transmit a service via two transmission paths protected mutually,
i.e., perform a dual transmission, in a second transmission
direction; and the second transmission direction is opposite to the
first transmission direction.
[0015] An embodiment of the invention further provides a device for
protecting WDM transmission, which includes, a
selective-transmission module adapted to transmit a service via one
path selected from two transmission paths protected mutually in a
first transmission direction, and a selective-reception module
adapted to receive a service via one path selected from two
transmission paths protected mutually in a second transmission
direction; and the second transmission direction is opposite to the
first transmission direction.
[0016] An embodiment of the invention further provides a system for
protecting WDM transmission, which includes a center node, a
distributor node and a terminal node; the distributor node is
connected with the center node via a backbone optical fiber, and
the distributor node is connected with the terminal node via a
distribution optical fiber; the distributor node includes two or
more permanent bridge connector, and at least two of which are
respectively used for a dual-reception downstream service and a
dual-transmission upstream service.
[0017] An embodiment of the invention further provides a method for
protecting WDM transmission, including: a terminal node detects
whether a fault occurs in a downstream service; if a fault
occurring in the downstream service is detected, the terminal node
identifies a downstream path in which the fault occurs, and
generates downstream path fault information; the terminal node
transmits the downstream path fault information to a center node
via an upstream path; and the center node switches the downstream
service from a working path to a backup path.
[0018] It can be seen from the above technical solution in the
invention, an asymmetric protection scheme is utilized in opposite
transmission directions, in other words, selective transmission and
dual reception is performed in a first transmission direction,
while dual transmission and selective reception is performed in an
opposite second transmission direction. This allows a distributor
node without a dedicated power supply or other equipments such as
air conditioners, so as to largely reduce the construction cost of
a WDM access network with protection function.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic diagram showing the architecture of a
WDM-PON;
[0020] FIG. 2 is a schematic diagram showing the architecture of
1+1 protection scheme;
[0021] FIG. 3 is a schematic diagram showing a system for
protecting a WDM working path provided in a first embodiment of the
invention;
[0022] FIG. 4 is a flow chart showing self-healing protection with
selective-transmission-dual-reception for a downstream service
provided in the first embodiment of the invention;
[0023] FIG. 5 is a 1+1 protection scheme of sub-network connection
provided in a second embodiment of the invention;
[0024] FIG. 6 is a schematic diagram showing an architecture of
WDM-PON network including a passive distributor node according to
an embodiment of the invention; and
[0025] FIG. 7 is a schematic diagram showing architecture of a
system for protecting WDM transmission according to an embodiment
of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0026] In an embodiment of the invention, an asymmetrical
protection scheme is utilized for a dedicated scenario of an access
network. In other words, in a downstream path (i.e., a path in a
first transmission direction), such a solution that selective
transmission is performed at a transmitting end and dual reception
is performed at a receiving end is employed; while in an upstream
path (i.e., a path in a second transmission direction opposite to
the first transmission direction), such a solution that dual
transmission is performed at the transmitting end and selective
reception is performed at the receiving end. In this way, a
selective mode is used for both the reception and transmission at
the side of a center node, while a permanent connection mode is
used for a distributor node near the side of users. The distributor
node implemented in such a way is not provided with a selective
switch, thus may be implemented with a passive device without a
power supply, so that peripheral devices such as air conditioners
are not required to ensure the working environment temperature and
moisture of the devices and equipments to reduce the cost. It is to
be appreciated by the skilled in the art, "upstream" and
"downstream" is opposite names which represent two transmission
directions oppositely. In the embodiments of the invention,
"upstream" corresponds to a first transmission direction, and
"downstream" corresponds to a second transmission direction
opposite to the first transmission direction.
[0027] Further descriptions will be made in the invention with
reference to the accompanied drawings and embodiments. The
permanent bridge connector may include a couple in the embodiments
of the invention.
[0028] A first embodiment of the invention provides a schematic
diagram of a system for protecting a WDM working path, as shown in
FIG. 3, Z1, . . . , Zn are a plurality of n terminal nodes.
[0029] A center node is provided with a WDM transceiver with a
plurality of wavelengths, a downstream transmitter 1 with a certain
wavelength and a selective switch module 101 a downstream service
is sent thereto. The two outputs of the selective switch module 101
are connected respectively with a Wavelength Division Mux/DeMux 1
and a Wavelength Division Mux/DeMux 2. The Wavelength Division
Mux/DeMux 1 is connected with a Wavelength Division Mux/DeMux 3 at
a distributor node via a backbone optical fiber as a working path,
and the Wavelength Division Mux/DeMux 2 is connected with a
Wavelength Division Mux/DeMux 4 at the distributor node via a
backbone optical fiber as a backup path. The downstream service
passing through the Wavelength Division Mux/DeMux 1 is inputted to
an input of a coupler 103 via the Wavelength Division Mux/DeMux 3,
and the downstream service passing through the Wavelength Division
Mux/DeMux 2 is inputted to another input of the coupler 103 via the
Wavelength Division Mux/DeMux 4. Finally, the downstream service is
outputted by an aggregate output port of the coupler 103 and
inputted to a downstream receiver 1 at a terminal node via a
distribution optical fiber.
[0030] An upstream service at this wavelength is in an opposite
direction to the downstream service. First, an upstream transmitter
1 sends the upstream service to the aggregate input port of a
coupler 104. Two same signals are outputted by two output ports of
the coupler 104 and then inputted into the Wavelength Division
Mux/DeMux 3 and the Wavelength Division Mux/DeMux 4 respectively.
The upstream service passing through the Wavelength Division
Mux/DeMux 3 is inputted to an input port of a selective switch
module 102 via the Wavelength Division Mux/DeMux 1, and the
upstream service passing through the Wavelength Division Mux/DeMux
4 is inputted to another input port of the selective switch module
102 via the Wavelength Division Mux/DeMux 2. Finally, the upstream
service is outputted by an output port of the selective switch
module and inputted to an upstream receiver 1 at the center node
via the distribution optical fiber.
[0031] Accordingly, the transmission process of upstream and
downstream services at other wavelengths is similar as above.
[0032] It can be summarized from the above description of the
embodiment of the invention that, in a first transmission
direction, a first node (e.g., the center node in the above
embodiment) transmits a service to a second node (e.g., the
distributor node in the above embodiment) via one path selected
from two transmission paths protected mutually, and the second node
receives the service via both of the two transmission paths. In a
second transmission direction opposite to the first transmission
direction, the second node transmits a service to the first node
via two transmission paths protected mutually, and the first node
receives the service via one path selected from the two
transmission paths.
[0033] In particular, by way of an example in which a first node is
a center node and a second node is a distributor node, in a first
transmission direction, the center node transmits a service to a
distributor node via one path, as a working path carrying the
service, selected from two transmission paths protected mutually
from the center node to the distributor node. The distributor node
receives the service via the two permanently connected transmission
paths from the center node to the distributor node. In a second
transmission direction (an opposite direction to the first
transmission direction), the distributor node transmits a service
to the center node via two transmission paths protected mutually
between the distributor node and the center node; and the center
node transmits the service to customer side via a path selected
from the two transmission paths as a working path.
[0034] It can be seen that, in the embodiment of the invention, a
passive second node may be provided using the asymmetrical
protection scheme in the different transmission directions.
[0035] The above Wavelength Division Mux/DeMux may be implemented
with an Optical Add/Drop Multiplexer (OADM) or a
Multiplexer/Demultiplexer (Mux/DeMux) unit; the selective switch
module may use an optical switch; and the Wavelength Division
Mux/DeMux and the coupler may be implemented in a single node or
separate nodes.
[0036] As shown in FIG. 3, when fault occurs in the working path
from the center node to the distributor node, fault detection is
performed at other nodes since the distributor node is passive and
unavailable for fault detection, and the center node is informed of
the fault for switching. In the technical solution shown in FIG. 3,
only the optical fiber from the center node to the distributor node
is protected, it is to be appreciated that the integral optical
fiber from the center node to the terminal node (i.e., a third
node) may be protected to extend the protection scope.
[0037] Concerning a downstream service from the center node to the
distributor node, because a fault detection unit simply exists at
an active node, the downstream service fault may only be detected
by the terminal node. A flow chart of an embodiment of showing
self-healing protection with selective-transmission-dual-reception
for a downstream service is shown in FIG. 4.
[0038] In Step 1, the terminal node detects whether there occurs a
fault in the downstream service.
[0039] A fault detection point may use one of the following
approaches for detection: detecting the power of an optical signal
split from that to be inputted to the receiving end; detecting
whether the service is present or correct using the receiver; or
detecting the dedicated overhead of the service to determine
whether the service is correct.
[0040] In Step 2, the downstream path in fault is identified and
downstream path fault information is generated.
[0041] In Step 3, the downstream path fault information is
transmitted to the center node via an upstream path.
[0042] The transmission of the downstream path fault information to
the center node may be implemented by using overhead information of
the wavelength of the upstream service, or using Out-of-band
transmission via an optical monitoring channel, or using a
dedicated alarm byte in the upstream service.
[0043] In Step 4, the center node controls a selective switch
module corresponding to the downstream path in fault to switch from
the working path to the backup path.
[0044] It can be seen from the Step 1 to 4 above, in this
embodiment of detection of the downstream service, the center node
performs selective switching for the downstream transmission path
based on the upstream path fault information fed by the terminal
node via the downstream path.
[0045] Concerning an upstream service from the terminal node to the
center node via the distributor node, the center node is provided
with a fault detection unit and also a selective switch module for
protection switching. Upon detection of a fault occurring in the
upstream working path, the center node controls the corresponding
selective switch module to select a backup path for single-end
switching.
[0046] In order to improve further reliability of a WDM
transmission system, a second embodiment of the invention is
provided with reference to FIG. 5 which shows a structural diagram
of a selective-transmission-dual-reception 1+1 protection system of
sub-network connection, where Z1, . . . , Zn are a plurality of n
terminal nodes, so that the protection switching may be implemented
not only when a fault occurs in the working path, but also when a
fault occurs in the transmitter or receiver.
[0047] The selective switch module here is located between customer
signal and a WDM wavelength transceiver. For example, a selective
switch module 111 by which a downstream service at a certain
wavelength passes may be implemented with an optical switch or an
electrical switch. Because the selective switch module 111 is
located in front of a transmitter, two transmission modules, i.e.,
a downstream transmitter 1W and a downstream transmitter 1P, are
provided at two outputs of the selective switch module 111 for
selective transmission of the downstream service at the certain
wavelength. The downstream transmitter 1W and the downstream
transmitter 1P are respectively connected with a Wavelength
Division Mux/DeMux W and a Wavelength Division Mux/DeMux P. The
Wavelength Division Mux/DeMux W is connected with a Wavelength
Division Mux/DeMux 3 at a distributor node via a backbone optical
fiber as a working path, and the Wavelength Division Mux/DeMux P is
connected with a Wavelength Division Mux/DeMux 4 at the distributor
node 4 via a backbone optical fiber as a backup path. The
downstream service passing through the Wavelength Division
Mux/DeMux W is inputted to an input of a coupler 115 via the
Wavelength Division Mux/DeMux 3, and the downstream service passing
through the Wavelength Division Mux/DeMux P is inputted to another
input of the coupler 115 via the Wavelength Division Mux/DeMux 4.
Finally, the downstream service is outputted by an aggregate output
port of the coupler 115 and inputted to a downstream receiver 1 at
a terminal node Z1 via a distribution optical fiber, so as to
realize the selective-transmission-dual-reception of the downstream
service.
[0048] An upstream service at this wavelength is in an opposite
direction to the downstream service. First, an upstream transmitter
1 at the terminal node Z1 sends the upstream service to an
aggregate input port of a coupler 116; two same signals are
outputted by two output ports of the coupler 116 and then inputted
into the Wavelength Division Mux/DeMux 3 and the Wavelength
Division Mux/DeMux 4 respectively; the upstream service passing
through the Wavelength Division Mux/DeMux 3 is inputted to an
upstream receiver 1W via the Wavelength Division Mux/DeMux W, and
the upstream service passing through the Wavelength Division
Mux/DeMux 4 is inputted to an upstream receiver 1P via the
Wavelength Division Mux/DeMux P; finally, the upstream service
outputted from the upstream receiver 1W and 1P passes through two
inputs of a selective switch module 112 respectively, and is
outputted from an output port of the selective switch module 112
upon selection, so as to realize the
dual-transmission-selective-reception of the upstream service.
[0049] Accordingly, the transmission process of upstream and
downstream services at other wavelengths is similar as above.
[0050] In the first and second embodiments of the invention, only
one distributor node is provided. However, in practical use, a
plurality of distributor nodes may be provided. In a WMD-PON
network architecture including a passive distributor node as shown
in FIG. 6, module 1, 2, . . . , M are a plurality of M distributor
nodes in the WDM-PON network, each of which corresponds to terminal
nodes from Z1 to Zn, and connects with a center node via a backbone
optical fiber as a working path and a backup path respectively.
[0051] An embodiment of the invention also provides a system for
protecting WDM transmission. Please refer to FIG. 7 showing a
structural diagram of the system for protecting WDM transmission
according to an embodiment of the invention. Here the internal
structure and connection relations will be illustrated in detail in
conjunction with the working principles of the system.
[0052] The system in this embodiment includes a first node and a
second node connected with each other via an optical fiber in a WDM
system. In particular, the first node includes a
selective-transmission module 71 and a selective-reception module
72; and the second node includes a dual-reception module 81 and a
dual-transmission module 82.
[0053] In a first transmission direction from the first node to the
second node, the selective-transmission module 71 at the first node
transmits a service to the second node via one path selected from
two transmission paths protected mutually, and then the
dual-reception module 81 at the second node receives the service
sent from the first node via both of the two transmission paths
protected mutually, i.e., performs a dual reception.
[0054] In a second transmission direction from the second node to
the first node (i.e., an direction opposite to the first
transmission direction), the dual-transmission module 82 at the
second node transmits a service to the first node via two
transmission paths protected mutually, i.e., perform a dual
transmission, and then the selective-reception module 72 at the
first node receives the service sent from the second node via one
path selected from the two transmission paths protected
mutually.
[0055] In particular, the dual-reception module 81 may include a
dual-reception permanent bridge connector; the dual-transmission
module 82 may include a dual-transmission permanent bridge
connector; and the selective-transmission module 71 and the
selective-reception module 72 may include a selective switch
module.
[0056] It can be seen from the structure described above, it is not
necessary for the second node to select the transmission path, but
keep a permanent connection. Therefore, the second node may not be
provided with a power supply device; thus may be passive to reduce
the total construction cost of the network. The first node in the
above system may be a center node in a WDM system, and the second
node may be a distributor node in the WDM system. Vice versa, i.e.,
the first node in the above system may be a distributor node and
the second node may be a center node. It is to be appreciated by
the skilled in the art that, when an asymmetrical protection scheme
is applied in different transmission directions in a system, one of
the nodes may be passive, and it is not intended to limit which one
of the nodes may be passive in the embodiments of the
invention.
[0057] An embodiment of the invention further provides a device for
protecting WDM transmission. The node device may be the first node
or the second node in the embodiments of the system. The internal
structure of the first node and the second node has already been
described in the above embodiments of the system; therefore it will
not be described here again.
[0058] The above description is only for exemplary embodiments and
not used to limit the scope of the invention. Various changes and
equivalent substitutions without departing from the technical scope
of the invention that readily occurred to the skilled in the art
shall be covered within the scope of the invention defined by the
appended Claims.
* * * * *